Wings, how easy/difficult, draggy/less draggy, pretty/ugly, twisty/stable?

 3 December 2021

Span wise ripples causes more drag, right? And having chord wise undulation is more like a plane's wing. Not saying it shall never be so, because span wise spar protrusions can become more acceptable for modelling metal cladded wings and it is easier to just place spars ontop of a ladder frame of wing planform?

1. Lay the leading, trailing, spar/s or no spar, wing tips.
2. Slot in sheet ribs, achieve flowing airfoil after covering. 
3. (con: the work involved in getting precisely cut sheet ribs)

1. Lay the leading and trailing edges and glue in bottom ribs as before.
2. Glue 1 spar.
3. Glue top ribs and achieve flowing airfoil after covering. 
4. (con: the work involved in getting precisely cut top ribs)

1. Lay the leading, trailing, wing tips and glue in bottom ribs.
2. Glue 2 or 3 spars on top and achieve a segmented airfoil after covering. 
3. (con: not so pretty)

With or without spars? With spar/s, covering top and bottom, more torsion resistance. Without spar, covering top or bottom, least torsion resistance.

Cambered ribs? Prettier, but camber may be inconsistent especially if ribs are bended, leading to warps. 

Solid modelling

 19 November 2021

I think the main difficulty with solid expanded foam modelling is the sanding required for proper shape and texture. However, if gloss over this seemingly inherent difficulty, expanded foam is about the lightest modelling material easily available for flying models.

The least work is profile planes. Where the wing and tails are to the planform without regard to the cross-sections and the fuselage is to side profile. In the case of light RC models, a profile fuselage is sufficiently strong and 'stiff', especially if wrapped with tissue or paper which takes care of the tensile and torsional strengths.

Next 'level-up' in aesthetic is to make the wings and tails airfoiled and to make the fuselage conform to the planform as well. The performance of the wings and tails are almost maxed out and the fuselage has lesser drag. 

The ultimate is to have the wings and tails tapered from root to tip in thickness and to have the fuselage conforming to cross-section.

Carving the wings with HWC is relatively easy but compound curved fuselage is difficult. Not all aeroplanes' fuselages have compound curves and some are easier to achieve by building up the fuselage cross-sections.

Instead of cutting fuselage to side profiles, some can be cut to the planform. In these cases, the planform fuselages can be stacked together to the depth required and cut to the side profile. Turtledecks and front deckings can be curled paper with some formers.

I wonder if it is easier to sand expanded foam (polystryene) in water. 

Don't forget that XPS can be sanded. However, if used in slab construction, it is probably twice as heavy as EPS. Depends on the density of EPS comparison.

 

Foam Cutter

3 November 2021

Making angle templates.

1. Draw baseline and angle on paper.
2. place straight template over angle.
3. tape wooden block over baseline.
4. snip away excess template material that protrudes from base of wooden block.

A pair will guide straight cuts to:

• wing roots at dihedral angle
• wing seat of nacelles to dihedral angle
• chamfered edges 

1 November 2021

Metal coat hanger, wooden stool, screws.

Why must making a vertical or inclined cutter involves drilling a hole on the worktop? It would be simpler if a metal frame is screwed to the underside of the wooden stool (or worktop), with the hotwire outside the wooden stool. The "C" frame may be held perpendicular or even alongside the wooden stool. To adjust the hotwire, slide it along the metal frame. Short circuit? That's what electrical tape prevents.

The same wooden stool functions as a worktop with feet. Being made of wood, it is relatively easy to screw in small screws to hold the metal frame. Since it is a worktop with feet, it can also be converted to a sheet cutter. Alternatively, the seating of the stool can be a worktop for temporary fixing templates to be used in conjunction with a separate bow cutter.

Main task is finding a wooden stool, an item that was easy to spot in the past. Now, plenty of plastic stools but difficult to find wooden stool. An alternative to a wooden stool is to find a wooden chopping board and use some rubber feet.

15 October 2021

Horizontal is vertical on its side. Cylinders and cones can also be cut with horizontal HWC.

Drop a bow cutter on 2 supporting columns from a workboard. Thin or thick sheets can be sliced to thickness, it became a sheet cutter. If a block is held between a C-Channel with pivoting grips/pins, rotating the foam block under the bow cutter can result in cylindrical or conical cuts.  

24 September 2021

Vertical or Inclined Cutter: Frame and Worktop

Construct a square frame with 4" x 4" clearance from 3/8" square wood. The 2 column pieces are drilled at both ends, The 2 beam pieces have additional drilling in the centre. The beams are bolted over the columns so the stretched hot wire is 3/8" away from the columns. To stretch the hot wire, pass the ends through the holes in the centre of the beam pieces, make loops and tension with rubber bands and a simple hook. Holding the square frame by hand, it is a hand-held cutter. If a floor is packed up across the columns to reduce the distance to the hot wire, it can be used as a sheet cutter. If a bed is attached with holes drilled to clear the frame and the frame is perpendicular, it can be used as a vertical cutter. Similarly, if the frame can be secured at an angle, it can be used as an inclined cutter. With a bed, circular objects can be cut if the bed is drilled to receive pivots, it can be used as a circle cutter.

Maybe this cutter and a bow cutter covers all my needs/wants.

23 September 2021

Bow Cutter: Beam and Levers

A simple 18" hot wire cutter for my small things.

A piece of 3/8" square can be the beam. Holes are drilled along the beam to attach the levers. The many holes means that the hot wire can be shorter.

Ice cream sticks can be the levers. Drill 3 holes in each ice cream stick, the central holes are for attaching to the beam, one end is for the hot wire and the other end is for the tensioner. Each lever is made from bolting 2 pieces of ice cream stick. A total of 4 ice cream sticks.

Assemble the beam and levers with 6 bolts and nuts. Wrap and coil the hotwire ends to the bolted levers. Tensioner can be rubber bands on the other end of the levers.

Wire the assembly and the hot wire cutter is ready for some low voltage current.

Hand-held Cutter

This is to cut foam with very short length of hot wire, maybe only 2"-3" and operable by 1 hand. It can be constructed like the bow cutter, just with a shorter beam of 3"-4". Useful for specific applications and since it uses the same levers like the bow cutter, the only additional work is making the short beam and a short hot wire.

Sheet Cutter: just a work top

This is to make thin foam sheets from thicker foam sheet. The basic idea is to have a tensioned hotwire separated by spacers to maintain the height off the work top.

A short plank or anything that is workable, rigid, and have a smooth and flat surface will do as the work top. I think 12" cutting length should be enough and since I wanted thin sheets, the surface does not have to be wide, maybe 3" is enough, anything wider is just more at ease.

If the worktop is thick enough to accept screws, then 1 can be screwed to grip the hot wire. At the other side, a short nail as a radius before tensioned by rubber bands to another anchor point.

Incline Cutter: Raking wire

The idea is is to hold the hot wire at an angle. And preferably adjustable angle at that, so maybe a work top is important. No idea how to do that easily yet.

Warren Truss

 28 October 2021

• Over the side profile of the fuselage, draw warren truss lines.
• Prepare strips of foam, lay down in one direction.
• Prepare strips of foam, lay and glue in the other direction. It is lap jointed to the first direction pieces.
• Lay and glue a side strip from nose to tail. This side strip is glued lap jointed to the second direction pieces.
• Cut the lattice to side profile, less thickness of outside edge.
• Remove from plan and glue another side strip to lattice pieces of the first direction.
• Glue edge strips around the lattice. 

Edge strips can be paper, card, foam, balsa.

In the simplest form, it is a I-section beam with side beams.

Side strips would preferably be from foam or balsa because some strength is needed. There may be more than one side strip on one side of the profile. 

Not Warren Trussed, a ladder framed I beam:

• Lay side strip on side profile.
• Lay and glue cross strips over side strip.
• Lay and glue another side strip.
• Cut cross strips to side profile, less edge strip thickness.
• Glue edge strips around ladder frame.

Why this method: lapped joints maximised resistance so it is equally strong and it is easier to make, easy to place reinforcement pieces, even if edge strips are weakened, the side strips are the main load bearers. 

Hot formed wet formed

 28 October 2021

Technique from Ralph & Paul Bradley for FAC no-cal?

Involves 1/16" sq balsa strip, wetted and then bent with low wattage soldering iron/pen. 

Seems to be a good method of making outlines without gluing short pieces to form the outline. 

The little 10gram RC flyers

18 October 2021

And now a Britten-Norman BN-2 Islander?

Expanded polystyrene foam throughout.

1/2" for fuselage, sliced to two sides, held apart with foam spacers, glued together at nose and tail, sand nose to shape.

Glue tube to nose with nose gear temporary inserted.

Cut tail from thin sliced foam or 2mm extruded foam sheets.

Cover.

Hotwire airfoil to wing, add ply dihedral (real one has no dihedral, the ply dihedral is T-shaped so it can be glued in a slot on the fuselage)

1/2" for nacelles, gouge for motors, insert wires to slits in wings.

Cover with tissue.

Glue tubes to nacelles with main landing gear temporary inserted.

Glue RC gear in fuselage and make access slot for 1s cell.

Insert nosegear and main landing gear to tubes. 

Use paper template to trace front shield, windows, door and other outlines.

Acrylic paint is good choice.

18 October 2021

How about a RSAF Skyvan?

Fuselage from 2mm foam sheets

Sides

Top and bottom spacers T-section

Wings from 2mm foam sheets

Whole planform

Balsa 1/8 sq leading edge

Balsa 1/8 sq spar capped with 10mm wide foam strip

No ribs except for roots and ends

Sand to shape.

Since fuselage is wide, can use V-section as dihedral brace with wings glued atop and then V-section brace inserted into fuselage and glued.

Tail

All from 2mm thick foam.

Sand to shape.

Nacelles

Rolled foam or thick foam

Lift Struts, Landing gear support, wheels, RC gear supports

Made from various thickness of foam

 Cover with tissue

22 September 2021

Make a biplane or just extend the wing tips? Maybe it will fly even slower?

Making it to a biplane seems a bit of work although the flying speed might reduce to almost half.

I could extend with paper wing tips stuck on with double side tape? Maybe another 2 inches on each tip? 7+4 = 11". Paper should be strong enough to cantilever 2 inches. 11x2.5 = 27.5 sq in, 27.5/17.5 = 1.57, almost 60% more area. Maybe I get to reduce the flying speed by 25%?

10 September 2021

The 1s 50mah cells dies too easily. I have the plane and controller but no usable cell. So I had to buy another because I saw Eachine has a similar one with 3 batteries. Price increased, but I had no choice. And today I noticed they dropped their price! haiz....

This is what I bought.

Apart from the decoration on the model and the controller (this controller has EACHINE silkscreened), it is the same. The 3 supplied cells are 75mah though (the 1 cell that KF606 was supplied with was only 50mah), I hope the 75mah cells will last and will not die off within a month. Included in the bag is 1 extra cell clip. The previous KF606 did not come with spare.

Use the components for a twin engine plane?

21 August 2019

I bought this from Banggood.

It is a 2 channel indoor flyer.

Wingspan of 7", chord of 2.5".

Without deducting the radiused wingtip, Wing area is 17.5sq inches.

How about using the components to build a Whitehead 21?

I printed the previous Whitehead drawing in A4 and compared it with the Banggood model. The wing area and propellers' diameter looks about right, but the tail area is much smaller than the Banggood model. The  fuselage is too small to accept the single cell of 50mAh and electronic unit. If I enlarge it to A3, there would be no problem for the cell and electronic but the propeller would be so small. I don't know if there will be sufficient thrust to overcome the drag.

If I were to make one flyable model:

1. Wings are constructed from tissue, preformed on mold. Each wing has a curved leading edge and 2 curved spars to occupy the 1st, 5th and 9th positions glued on top of the preformed tissue. Spars at the 2nd, 3rd, 4th, 6th, 7th and 8th are representations, e.g. with strips of paper for a bit of stiffness to the tissue surfaces.
2. Photos of the original shows cambered horizontal tail but I will choose to make it flat for down pressure to increase dynamic stability. Ideally, the CG should be like a flying wing, but because of the camber in the wings, this would be too instable, so the CG has to be brought further forward and the horizontal tail at a negative incidence. Construction would be 2 leading spars, separated and stabilized by one spar. The other spars will be represented again on tissue before the spars are glued on.
3. For the fuselage. I want rolling wheels and easy access to the single cell and control unit. I don't know how I want to do that. Block of polystyrene covered with tissue? Paper is weight and will crumple easily.

28 October 2015

There's dihedral but no vertical fin/rudder. If I were to make one flyable model, the wing could be cut from 3mm foam sheet, linked by a pair of wire joiners to form the dihedral. The horizontal tail is similarly cut from 3mm foam but seperated to form a single elevator. A vertical tail and rudder can take the shape of half the horizontal tail. The wing and tail are glued to a box fuselage. A beam for the two 7 mm motors and hubsan propellers, wired up to a single plug that fits the WL929 939 board, should be glued onto the box fuselage and the battery goes under the receiver board, into the box fuselage. 2 pushrods are then connected to the controllable tail surfaces and the exposed servo horns. Finish up with bamboo bow and mast, complete with strings and wheels and a standing pilot with a hand holding onto the mast.

Electric over Glow

 25 October 2021

The model

Unlike glow fuel, electric does not have oil, does not need fuel proofer, does not need cleaning, any paint is ok.

The battery can be positioned to change the CG.

Motor direction can be changed easily.

The flying

The motor starts on demand and power is proportionally delivered, very convenient, doesn't cut off unexpectedly, is quieter and safer.

Electric may not have the same power as the voltage drops but we have throttle for that.

The CG doesn't change with electric models unlike glow fuel.

Less vibration, easier to have the prop spins true.

Other quirks

Power density is lower than glow fuel but the 'full-bore' appears higher.

Once out of the factory, the battery dies very quickly. Glow is similar, it attracts moisture, nitro evaporates, but has much longer usable lifespan than battery.

One battery is only one flight and that battery has to be recharged which takes about an hour whereas glow fuel is filled within minutes.

Battery is more expensive than glow fuel, although engine is more expensive than motor.

Propeller and shaft for rubber

 23 September 2021

Ideas for material of the propeller, shaft and bearing for small rubber models:

• malleable wire from a small paperclip for shaft, shaft bearing,
• plastic tubes from cotton buds or ball point pen for propeller hub, shaft bearing
• balsa for propeller hub and blades,
• other wood (bamboo, bass, chopstick) for propeller hub,
• cardboard for paddle blades,
• foam or plastic cup for propeller blades,
• ??

I think it is ok if the propeller hub is strong and heavy, plenty of hits and noseweight usually needed anyway. A malleable shaft means it will be easier to adjust it straight again, spring steel is too difficult to make and to correct. A jig is needed to check symmetry, for sanding angle flats and gluing blades. 

No such problems if capacitor powered.

Sniffi, review of a balsa glider

Gone (22 Sept 2021)

Lost over fence of adjacent condo last Sunday. That's the end of it.

Needed up substantial up elevator and left rudder, flies too fast. Doesn't recover well, seems the dihedral and rudder are too small. Definitely not roll off the top model.  Would prefer catapult launches.

Do it again? nah.... wasn't forgiving and flight times quite short even on occasional good launches.

Last point: don't use UHU APG for this, bendy joints.

Before flying (14 Sept 2021)

This Ikea plastic laptop table worked as a work bench for this model. 

I used double-sided tape on the edges to hold the balsa parts for planing and sanding. 

It is still available from Ikea, Klipsk bed tray at $13.90.

I planed too much off the port wing tip. Having the balsa grain going outwards is not a sure fix.

I don't have 'resin glue' at hand, so I used UHU All Purpose. Result: the joints remained flexible for a few days after gluing. The fin was glued ok, it stiffened the quickest because it was so easy to sand the edges square. The polyhedral joints do not have matching joints, it wasn't easy to sand at approximate angle, so more glue filled the gap and it takes a longer time to stiffen, currently, 3 days has lapsed and I think it may be ok for launching. To play it safe, I am giving it a few more days.

The decorative strips cut out from the plan were glued with white glue to the sanded model. I didn't have glue stick at hand and tried successfully with white glue on the small logos of 'Aero-naut' to the fin. However, the rest of the decoration wrinkled, white glue is not suitable, I might have had better success with UHU All-Purpose Glue (UHU APG).

The tail jig set the horizontal stabiliser square and the fuselage vertically to receive the wings. The dihedral jigs were spot glued to the wings' underside, and then the wings were joined to the fuselage. The mini-plane rested over the dihedral joint to keep both wings pressed against the mounting area. I left it jigged like that for 2 days to allow the UHU APG time to harden.

After UHU APG has stiffened enough (feeling a bit springy at the dihedral joint with light finger pressure), I did "bed-glides" by launching the model over my bed towards my pillow. The diving glides indicated that the single lead piece provided in the kit is enough. That is good news. It is not time to give it up-elevator yet, during the bed-glides, I noticed it was turning to the right. Slight bend at the fin seems to straighten the glides but the starboard wing hung low. Putting the model on the floor had the starboard wing down on the floor. Balancing the model inverted on my fingers confirmed that the starboard wing is heavier, the CG is to the right side of the fuselage. This is probably due to the different balsa density between the two wings. Since my port wing and tail have their tips planed off, I think I will glue a paper wing tip to the port wing to reduce the mass offset but I will leave the port tail alone.

I may remove the wrinkled decorations, it would be easy, just moisten with water and perhaps a few passes with a sanding block after the model is dried. I want to try with it on first.

At the beginning (6 Sept 2021)

This is my ongoing review of Sniffi. I got Sniffi from Rotor. It seemed simple enough, but I over-estimated myself and had to pick up lessons along the way. It has been a long while.

The kit was die-cut, everything seemed to be there except that I only found a small piece of lead, the larger piece indicated on the pictorial instruction was not found. I don't think that will be enough but since that was what I received, and the lead weight is to be concealed, I am trying it out with just one small lead weight and didn't source from my collection.

A curious warning on the instruction pamphlet says to use resin glue and not wood glue for the fuselage pieces. Perhaps the concern is warpage? Since this Sniffi appears to be a German Kit, I am going to use UHU General Purpose.

The CG indicated in pictorial instructions is confusing, I hope it is 20mm in front of the trailing edge? This would be the first time I will have a glider with such a rearward CG.

The balsa pieces were cut through, the pieces were crushed on the entry side but thankful that the exit side was clean.  The wings and tail is only of 1/16" thick sheets. Mine had hard balsa for the wings and soft balsa for the tail and fuselage. I think the wings ought to be of lighter balsa and the fuselage pieces would require heavier balsa. I suppose the heavier wing is ok because the CG seems to be near the wing's trailing edge.

I wanted to use the clean cut edges for the bottom of airfoil because I figured that some sanding on the crushed top side will make it look alright. But this is not possible for the port wing because of how the pieces are laid out on the balsa sheet.

I wanted the tail to be of lifting section, with the fin lifting to yaw the plane to circle left. I also thinned the tips to reduce the tail's weight further. Thin trailing edges allow for future adjustments, there will be a gap between the fin and elevator, better for adjustment I hope. 

I wanted the wing to have a sharper leading edge and thin trailing edge. I wanted the tips to be thinned outwards. 

Lessons learned:

• One elevator tip was cut too deeply. Only plane in the direction where the wood grain will throw out the planer, that way, it will not dig in. Even if it meant that I am planing towards myself. 
• Use new sandpaper. I was using old sanding blocks and it doesn't cut the balsa.

Positioner for small objects

 16 September 2021

Idea 1

Material: 2 ice-cream sticks, 3mm thick scrap piece, one rubber band.

Make it:

1. Glue or tape 3mm thick scrap piece to one end of a ice-cream stick.
2. Place 2nd ice-cream stick over the 1st.
3. Loop rubber band over the ice-cream sticks in the middle.

It becomes a flat pincer for holding upto 3mm thick objects.

Constant grip/clamping force.

Idea 2

Material: 1 ice-cream stick, double sided tape.

Make it:

1. Lay double sided tape to one end of ice-cream stick.

It becomes an extension arm of the small object stuck to the sticky end.

Delicate grip, easily removable when small object is secured by rocking it off. 

Receiving a receiver today

16 September 2021 (latest)

I received the receiver. It is too small to fit in the connecting pins, the spacing looks to be around 1mm.

I wonder how to solder.

The holes are small, I don't think my wires are that small. Maybe I have to solder the wires to small diameter pins and then solder the pins to the receiver. I wonder if a staple pin is small enough to fit in the holes and if it can be soldered. 

I also remembered I have magnet wire, un-used in a coil that I purchased a long time ago. It looks like lacquered single strand copper wire, maybe I can use that?

But do I really want to cut off the servos' connectors?

10 September 2021 (earlier)

AEORC RX346/T 2.4GHz 6CH Mini RC Receiver with Telemetry Integrates 2CH Electromagnetic Servo Controller and 1S 5A Brushed ESC Support FlySky for RC Drone - Without Telemetry

I am going to receive this receiver today!

Brand Name: AEORC

Item Name: RX346/T Receiver

Model: RX346/RX346-T (with Telemetry)

Weight: 0.5g

Size: 16*10*2.5 MM

Working Voltage : 3.0V-4.2V

Automatically match frquency

Integrated 2CH Electromagnetic Servo Controller and 1S 5A brushed ESC

Support FlySky Transmitter

I already have something like this:

The ones I had, have grooves in the female housing as well, similar to the male pins. I think it meant I can break it into the number of channels that I want.

If it fits into the holes in the receiver, I wonder if I can use them to connect the battery and the power supply to the servos.

The obvious drawback to using these connectors is the size, weight and maybe I lack the ability to do it nicely. The manufacturer have designed it for direct soldering and I am complicating things for myself.

How do I wire it up? For use as a 3-Channel receiver maybe I would disregard the Magnet servos and Ch1, Ch5 and Ch 6. Ch1 is disregarded because it is on the other side of the receiver whereas Ch 2 and Ch 4 are adjacent to each other.

Soldered at receiver: 

A) 3 male prongs for GND-, 3.0-4.2V VIN+, CH1 (PWM OUT); (solder CH1 just in case) 

B) 2 male prongs for GND- MTR, VOUT+ MTR;

C) 2 male prongs for CH2 (PWM OUT), CH4 (PWM OUT).

Soldered at each of the 2 servos: 

Signal is female pinned to plug into C,

GND-, VIN+ are male pins to connect to busbar adapter.

Soldered at the motor:

2 female. These plugs into B of the receive.

Busbar Adapter for 1s Cell 

The 1S cell will have a pair of female connectors (right in the photo below) to plug into a pair of matching male connectors (left).

In the photo above, the battery (1S cell) will come with the female connector as shown on the right. The male connector as shown on the left is usually directly soldered to the receiver. For our purpose, strip the ends of the 2 wires of the pair of male battery connectors to solder to a pair of busbar adapter.

The busbar adapter block is a pair of 3 female pins.

The wires are soldered across 3 female pins.

These female pins will supply power to receiver and 2 servos.

 

How to plug them together?

• Plug power leads of the servos to the busbar (check polarity).
• Plug busbar to the receiver (check polarity).
• Plug motor to the receiver (check polarity).
• Plug signal wires of the servos to the receiver.
• Mount the receiver on model (because the connections will increase the height by a lot).
• Plug 1s Cell to the busbar.

Footprint of receiver (UNCERTAIN)

Getting every connector on top of receiver

It will not be possible to plug the busbar over the receiver because the servos' power leads will be in the way.

Bending the legs of the GND- and VIN+ inwards over the receiver may not be feasible.

Getting connectors to cross over the receiver

Bend legs of the GND- and VIN+ outwards, legs of the PWM in the same direction (both will be alongside the GND- and VIN+).

Do the MTR connectors interfere? Solder on the other side of the receiver?

2mm depron glider

 13 September 2021

I still have a few sheets of 2mm extruded polystyrene (can't buy it here now) and I could spare one to make a few chuck glider. The main advantage is it is light.

There is grain to the polystryene, cut wing in one piece, cut horizontal tail and vertical fin. Maybe can use Sniffi as a template.

For polyhedral, don't cut the wing, bend it. It will be floppy but it might be enough. At least I will not be adding weak points and weight. Either bend it over a straight edge and it might be too floppy, then I guess I can try to stiffen it by applying 2 strips of paper to both sides. Or, over a round dowel and heat applied to the foam to help it go round.

hmm, maybe a piece of tape on the bottom and a paper strip on top is good. I'd rather the foam compressed than having it cracked.

Shape a short strip of balsa and glue it to a long strip to give it more strength at the wing's leading and trailing edges. Shape and sand smooth the fuselage and add nose weigh and catapult hook. Be generous with the catapult hook because it is located at the nose and weight is useful there. 

Osprey 1

13 September 2021

I placed my order for another Dart 280 last month. Shipment was delayed to 12 September 2021 and I had received other items I ordered on that day. I checked the status today and shipment date was indicated as 21 September 2021, and I have the option for a refund.

19 July 2021

Some days before 17 July 2021, I trimmed the pylon down to the motor because it looks better. I also checked that all controls are working.

On 17 July 2021, I placed the 1s cell in the side pocket and just infront of the servos, the CG seems ok and I tried a test glide. It glided well enough and I didn't need more test glides. I didn't have to do any adjustments for my test flights. And then, surprise surprise, the motor didn't start even though the rudder and elevator servos were working. Quite a dampener

Perhaps the Dart 280's receiver isn't too durable. What shall I do now? Buy another Dart 280 just for the receiver, servos and motor? I recall that the Dart 280's servos didn't plug into my other micro receiver. 

5 July 2021

Ready for test flight and trimming on 17 July 2021.

I had to use bamboo to stiffen left-right distortion.

I used old carbon pushrods but they were too short, so I pulled the z-bends out and fabricated longer z-bends. Hopeful that it will hold up until trimmed.

I used Dart 280's receiver, servos, motor and cell. The receiver's battery plug's housing will pull out from wires if not careful. The motor lead wires were short, at one time I connected an extension lead, but after realising the CG was too forward, I used a smaller 1s battery and used double-sided tape to mount the receiver and motor on the pylon. 

If I need to adjust up/down thrust, hopeful that double-sided tape allows this flexibility and will hold until trimmed.

Hoping it is light enough for indoor flying in Kembangan CC.

16 June 2021

After the servos were glued, interest dwindled and the project stalled.

I still need to:

1. Hinge the elevator (horn already glued in)
2. Make the slot in the fin and glue the horizontal tail (I have to decide how much decalage)
3. Hinge the rudder to the fin (horn already glued in)
4. Fabricate and connect the pushrods
5. Make the slot in the pylon for the pusher (I have to decide the thrustline height and downthrust)
6. Make a hole in the wing for the motor plug
7. Pass the wing through the pylon and glue
8. Glue the motor (motor wire may be too short, I have to decide the side thrust)
9. Glue the motor doubler
10. Connect up and test

22 February 2021

10 minutes just to clear a workspace, finding stuff and tape the plans together.

40 minutes to mark out and cut out the blanks for the wings (grooved) and fuselage.

 

2 February 2021

Osprey 1 is a homebuilt type of seaplane that seats one and it had the engine on a pylon turning a pusher propeller. There is a plan on outerzone for a CO2 power free flight model and it is at 18" wing span. 

I wanted a slow indoor flier that uses the motor prop, receiver and servos and perhaps 150-400mah 1s cell. The electronics are from: Jumper W280 Dart 280mm Wingspan Indoor Park Flyer Mini Paper RC Airplane BNF for Trainer Beginner. I didn't get my Dart to fly reliably before it was damaged and didn't want to put in further effort. This is because the dart has a lot of drag, the planes are at 2 angles the wing portion at one angle and the fuselage portion at another. I don't like the waste of thrust and the model is not efficient.

I don't want to follow the outerzone plane faithfully. I will probably run out of steam. My desired construction is:

1. Profile 3mm foam fuselage with integral pylon, fin and rudder. Left side pretty, right side all the stuff and pushrods etc. Use a bit of weight at the left wingtip to counter balance.
2. Flat plate cranked wing of 3mm foam. It slots through the fuselage's pylon. 

So here goes, starting with the wing (because the wing seating on the fuselage has to match the airfoil shape (cranked flat plate)) :

1. Mark out the wing blank: 1) at the bottom, the slot, the polyhedral joint, 40% chord line for cranking; 2) at the top, the tip panels' polyhedral joint. (15 mins)
2. Cut the wing blank, the slot. (5 mins)
3. Groove the underside, raise the trailing edge (upside down), hot glue to set the crank. (5 mins)
4. Cut from bottom the polyhedral joint line. (2 mins)
5. Flip tip panels top side up, cut at angle the polyhedral joint line. (3 mins)
6. Flip mid section wing top side up, set the two tip panels to the right angle, glue together. (10 mins)
7. Sand the whole wing, matching up the polyhedral joints and rounding the edges. (15 mins)
8. Apply thin vinyl tape to reinforce the polyhedral joints and leading edge of wing. (15 mins)

70 mins

Now that the wing crank is set, it can be measured and transfer to the fuselage profile. I wouldn't use the raked fin and rudder on the Osprey 1, because I prefer to have the pushrod more perpendicular to the hinge line. 

A slow flying model at low throttle means the wing has to be big but this is not possible because I have to maintain the planform shape and size. To increase lift, I am using the cranked airfoil and presenting the wing at a positive angle of incidence. To maintain the angle of attack of the wing I have to use the stabiliser, so I must present the wing/stabiliser at a slightly greater decalage. I will take the stabiliser at zero degrees to the direction of flight. I will present my wing at 3 degrees. The propeller is mounted above the wing and will have a strong nose down moment. I will present my motor at at positive 6 degrees to the stabiliser.

1. Mark out the fuselage blank. (10 mins)
2. Cut the fuselage blank, separate rudder and cut slot for motor. (10 mins)
3. Sand the fuselage and rudder blanks. (10 mins)
4. Mark out the stabiliser blank. (5 mins)
5. Cut the stabiliser, seperate the elevators. (5 mins)
6. Joiner to the elevator. (5 mins)
7. Hinge the elevator to the stabiliser. (5 mins)
8. Apply thin vinyl tape to left side of fuselage, fin and top side of stabiliser. (10 mins)

70 mins plus 60 mins.

Follow by:

1. Glue the horizontal stabiliser to the fin. (5 mins)
2. Glue the wing through the fuselage pylon. (5 mins)
3. Mark and cut the engine blank. (5 mins)
4. Glue the motor to engine blank. (5 mins)
5. Sand the engine blank. (5 mins)
6. Glue the engine blank assembly to top of pylon. (5 mins)
7. File slot so that the motor connector can pass through right side of wing. (5 mins)
8. Apply thin vinyl to pylon to hide the motor wires. (5 mins)

130 mins plus 40 mins.

Finally, glue receiver, servos, horns, making up pushrods etc. (60 mins)

Total time will take 170 mins plus 60 mins = 230 mins or 3 hours 50 mins. Can be built in about 4 sessions.

Motor mounting for geared coreless motors

10 September 2021

I read through some articles on constructing Peter Rake's mini RC models on outerzone and found that he designed the motor mount either vertically with a hole to fit the motor or horizontally with a slot to receive the motor and one builder used Goop so that the thrust line can be adjusted.

Maybe I can use UHU or epoxy to glue the motor cylinder to my mount.

What a simple idea and I didn't think of it.

29 March 2021

The cheapest geared coreless motor unit does not have a horizontal flange to mount the on the model. I have a few ideas to mount the geared coreless motors:

• Bulkhead
• aluminium bracket
• square section rod

Bulkhead

Make a hole in a thick slab of foam or 2 pieces of ply to fit the nylon housing. Enlarge hole to clear propeller bearing. 

If the block shall also be the nose block, such as is possible with blue foam slab, then the hole will be at 2 angles and not perpendicular to the block, to cater for side-thrust and nose-thrust. The big propeller gear will be exposed. The motor unit slips in from the front with the propeller already pressed fitted.

If the bulkhead shall only be to mount the motor unit, then the hole can either be perpendicular with the sides of the block bulkhead sanded to the thrust line or in 2 bulkheads system, by positioning the holes differently or as per the first option of single slab bulkhead, to have the sides squared and the hole at the tilted angles. The motor unit slips in from the front.

Either way, the motor unit is glued to the bulkhead/s.

Aluminium bracket

Cut strip of aluminium from an aluminium can. Coil strip around diameter of nylon housing then bend 2 tabs so it is a half bracket.

Internal flat bulkhead to support bracket will be needed.

Since the aluminium is so pliable, it can be twisted to the thrust line many times by hands.

The aluminium half bracket will be glued to the nylon housing. Roughening the contact surfaces may also allow hot glue to be used.

Square section rod

Each housing has a small 2x2 or 2.5x2.5mm square hole.

If I can find a stiff enough square rod, then I could have this as a single beam across 2 perpendicular bulkheads.

There will be minimal contact area at the bulkheads, so an alternative is to glue it to a horizontal bulkhead.

If the square rod can be bent by hands, then it can be bent to the thrust line many times too.

A further option is to glue the square rod to a flat strip and use that instead. 

Sanding Tools

 2 September 2021

Sanding jig (1) for square balsa strips

1. Base piece from ice-cream stick, 2 cm long
2. Pressure piece from ice-cream stick, 2 cm long
3. 2 scrap balsa thickness spacer
4. Sand paper 150grit, 250 grit  
5. Double-sided tape

Lay double side tape to 1.

Lay sand paper stick to 1.

Lay double side tape to edges of sand paper stick.

Lay 3 to edges of sand paper stick.

Lay 2 over 3.

Squaring balsa stick/s

Pinch jig to grip balsa stick slightly

Pull stick

Reverse edge.

Sanding jig (2) for square balsa strips

1. Sanding block with sand paper 150 grit, 250 grit
2. 2 scrap balsa thickness spacer
3. Double-sided tape

Lay double side tape to 1.

Lay 2 on tape.

Squaring balsa stick/s

Lay double side tape on table.

Lay sticks on tape.

Lay jig over sticks.

Slide jig over sticks.

Lift sticks and reverse edge.

Sanding jig for balsa ends and edges

1. Rectangular piece of ply (harder than balsa), 1 side straight edged
2. Square piece of ply, each side is the width of the rectangular ply piece
3. 45-90-45 triangular ply piece
4. Base piece with length same as item 1 and width is 2cm wider than item 1
5. Sanding blocks, 150grit, 250 grit  
6. Double-sided tape

Glue 1 on 4.

Glue 2 on 1.

Lay double side tape to 1.

Sand balsa stick/s

Item 3 sticks on double side tape to hold balsa stick/s at the angle.

Lay balsa stick/s on double side tape between 2 and 3.

Slide 5 along 1.

Sand balsa formers straight

Lay balsa former blank over item 1's straight edge.

Slide 5 along 1. 

Sand balsa/foam discs

Pin blank at set distance from edge of 1.

Slide 5 along 1.

Repeatedly lift and rotate blank and slide 5 along 1.

Sanding around coins and other round object

1. coin or other round object (harder than balsa)
2. double side tape

Lay 2 on 1.

Sand discs

Lay balsa/foam on 2.

Slide 5 around 1.

Shoot!

 11 August 2021

"Shoot!" is a catapult glider for good easy flying. It may be launched by throwing, but each throw will be slightly different from the last, in speed, attitude and tilt. It is much easier if it is rubber catapult launched, the force/speed can be held constant and repeatable, the attitude and tilt is easier to maintain.

It is meant to be flown indoors. The space and ceiling of an indoor venue is limited, so the glider has to be able to transit into tight circling glide easily. Easily available are those short rubber bands, stretched all out, they can't shoot to the ceiling height of KKCC sports hall. The glider has to be light to fly slowly, powered by a single or a double rubber band, easy to construct from easily accessible material, easy to trim and highly stable in no particular order.

I'm thinking of a 5g glider:

• paper clip for catapult hook and partial nose weight, held with heatshrink sleeve on the nose of the dowel fuselage with drop of superglue;
• remaining nose weight is solder wire (easy to coil around paper clip, snip shorter or coil another piece);
• something to make the nose bigger for safey;
• 2mm bamboo dowel for fuselage (shaft), extending past the tail to provide pull back grip;
• short plastic sleeve to slide over the shaft (adjustable wing position/CG, may be superglued after CG is determined), epoxied to aluminium dihedral strip (comes from aluminium soft drink can);
• Simple but ample dihedral (Polyhedral too much work) so it can also transit by rolling over;
• Wing of 3mm foam for front 50% chord and tips, photocopier paper for 110% chord (the 10% is wrapped over to the top of the wing);
• Wing shape has swept back;
• Tail pieces similar to wing's construction but thinner foam.

No RC? How about free-flight?

11 June 2021

Wheels

Now if the wheels are represented by rings, then there is nothing more to do unless I want to include the hub or to colour the tyres.

However, if the wheels are made from 1.5mm foam sheet sanded around a 10 cent coin, I could colour the tyres by making a tool to hold the pen at a distance from a guiding surface and use the tool to draw in the tyre ID. Then, I thought again that that is simply too much work when I could have just used a circle template!

 

7 June 2021

Farman Moustique

Engine block: a hexagon cylinder measuring 12mm across, so that makes it 6mm each side, 10mm depth made from 120gm/m2 green coloured construction paper. I originally thought of making it from 1.5mm foam strip, taped on the inside, scored on the outside, roll up and then cover with silver tissue on outside. This idea was not taken up because paper is strong enough. A tip is to use a circle template so the hexagon can be set central and not skewed.

Cylinders: A 6mm diameter, 10mm long. Flatten a transparent drinking straw, cut the 'slots' and tend roll back to cylinder shape 10mm high. Two loops to represent the cylinder and one loop on the other end to glue to the engine block. I didn't use bendy portion of drinking straw because I don't have them. I didn't use thread to simulate cylinder's fins because I remember it was time-consuming, messy and not visually impactful.

Wheels: 3mm wide x A4 length green construction paper rolled around an inside former. Failed attempts include: 1) tapering the 3mm wide strip on both ends, hoping to get a round cross-section; 2) using circle template (18mm diameter) as an outside former. An idea was to use circle template (18mm diameter) as an outside former but use two 3mm strips of flexible foam, one inside the other which seems messy again and difficult to get them round. I also tried to double side a 10cent coin on a 3mm foam piece, sand round (too button-like). Maybe can try again with the 10 cent coin idea but with thinner 1.5mm foam sheet but the result would be foam discs. 

These parts are small, they are difficult to make accurately and any little deviation is obvious.

They are time consuming, it took me hours because they are such fiddly little things for my fingers.

28 May 2021

On the peanut size Farman Moustique capacitor free flight :

• Drinking bendy straws for cylinders with paper hexagon crankcase.
• Joss-sticks for leading and trailing edges for wings.
• Foam strips for ribs.
• Drinking straw strips snaps back when bent. Can use it to make frames for landing gear, stabilisers, cabanes and perhaps tail skid (simple stick type, not the sheet type shown on plan). Can also be used to bind to motor?
• Thin wire mount can be bound to motor so that thrust-line can be adjusted..
• Circle template to make wheel laminate.
• Coin template to sand wheel discs.
• Foam fuselage can be slit so that the dihedral can be set. 
• Paper propeller blades for static display (with double side tape to stick temporary to actual propeller).

7 May 2021

As a first OD FF, maybe I should focus on getting maximum flying ability instead. It won't look good, but it should be light and easily adjustable.

Here's some ideas on basic adjustability for a free flying model.

• Motor on a 180 degrees wire bend. Side-thrust, down thrust.
• Wing posts on "H" carrier. CG, incidence, decalage, wing tilt.
• Rudder on a wire.

5 April 2021

Farman Moustique!

Found the charger of the supercapacitor free flight model from Banggood.

So it has been a year and a half. The 3 batteries are still there and it still works.

I thought about how to mount the motor. I could glue short T-sectioned foam batons to the motor to form the hexagon crankcase. Then I thought that I could just have a small hexagon foam section with a center hole to receive the motor. I looked back through my postings and rediscovered I had thought about this before, "The motor can be directly glued to a hole in a foam block, ..."

Look at the date, it's quite some time ago!

11 December 2019

I am going to use the electric components from a supercapacitor free flight model from Banggood and graft them to a model of fancy. I will then not need to understand how the electrical/electronic components work, and not need to source the component parts and soldering them together. Seems easy enough and I can focus my limited time to making cute-sy models! 

I think the size of the model will be around the Peanut scale. There are definite advantages of using supercapacitor over rubber for that size.

The structural requirements are simpler; there is no compression and torque from the rubber motor and there is no need to build around the rubber motor (no cavity needed for the rubber motor).

The model can be made from lighter material such as sliced foam, paper and tissue which are conveniently available and much cheaper too!

Another convenient feature is that the model is charged in seconds, instead of winding it up.

And I think that the rubber motor and propeller assembly is as heavy as the complete supercapacitor setup, if not heavier.

And because of its compactness, it is a breezy affair to have the CG forward; it really opens up short-nosed choices and those that would otherwise require a protruding motor stick for the rubber motor!

The motor can be directly glued to a hole in a foam block, or indirectly to a flat piece which acts as a motor mount and which is then subsequently spot-glued to 'engine beams'. The idea of a motor mount is to have adjustable thrust angle.

The charging point will need to be conveniently and securely located. However, it is so small and light and so would not be an issue. Actually, I think dangling it from the model is fine too.

Now, the propeller will be disproportionately small, relative to the size of the model. A rubber powered propeller is disproportionately large. View this as a bonus, the landing gear can retain its scale. If a scale sized propeller is desperately required, there are at least two options: 1) geared motor, or 2) affix scale sized blades for 'static' display using double-sided tape at the back of each blade. Unless there is too much spinner/cowl area for he smallish propeller, I am sticking to option 2 for it is so much simpler.

2 December 2019

Which best represents?

Wouldn't one like to get maximal effect out of minimal effort? I know I would. But in order to do that, let's understand that we should not insist on perfection. A model is only a shallow representation and it will never amount to the real thing; there will always something imperfect if you look deeper. Since they will never be literally perfect, I would rather save my effort and spend them on areas that gets the maximal effect.

In order of 'importance', generally:
Fuselage and fin:

1. side profile, 
2. cross-section,
3. planview.

Wing and elevator:

1. planform,
2. dihedral,
3. airfoil.

So it's the 'shape' that we tend to view to be the most important. We enjoy looking top down at the model too, so the top surfaces wins over the bottom surfaces. There will always be exceptions and some other parts are also very 'characteristic--al' , if the real aircraft has struts, wheel pants or exposed engine cylinders, we cannot avoid making them.

Summary of thoughts on foam modelling

25 May 2021

• Sanding is unavoidable in most instances. Protrusions outside the intended outline can be sanded away slowly until it fits exactly. To minimise sanding, cut to the edge where possible to have a vertical cut. 
• Straight lined cuts are the easiest to control using straight edge and it is easier to judge whether the cutter is held vertical even though the cutter is held at an angle to the direction of cut.
• Segmented lines will approximate curve.

As an example, it is easier to make flat discs resembling wheels by dotting the the centre point of the blank and use a straight edge to make straight cuts around the wheel outline. Alternatively, a simple tool can be fabricated to pivot on the centre point.

Sounds a lot of work, it would be best I suppose, if I have a suitable 'wheel-template', such as a coin or washer that is of the diameter desired. I could then use double side tape to fix it to a blank, slice with cutter since the cutter can not cut through the template. And the sanding finish would be easily performed. Once the template is removed, place the disc in a suitable sized circle template and mark out the center. 

18 September 2018

It is good advice to think things through, and writing the thoughts down helps to consider any issue objectively. That is, except when I start to over-think and complicates matter simply because what I thought was logical can be so impractical. Well, that's the way I am. Less think more action might be an improvement but I still like to write about it, isn't this what a personal blog is for? A diary of thoughts. Here's how I am thinking of modelling foam. Nothing on wings, they are quite straightforward.

Fuselage

1. Measure the length of the nose to the extreme tail end of the fuselage. If there is a spinner, exclude it. If the rudder shall form part of the tail end, include that in.
2. Measure the maximum height (depth) of the fuselage. If I will be using sheet foam for fin and rudder, than they shall be ignored.
3. Mark out the measured length and height on a polystyrene foam board that is thicker than half the fuselage width. In this case, the foam fuselage shall comprise of a left handed half and a right handed half.
4. Cut two rectangular blanks. To make them identical, use squares and hotwire cut. Mark the datum line on the left and right blanks.
5. Glue the plan view of the fuselage onto thick cardboard. Cut only one side of the curved planform so that there is one convex edge and the opposing edge is straight and parallel to the centre line and to the full depth of the foam board. Make 2 sets if the foam will be cut free hand using a hotwire bow. If a table hotwire is used, it might be possible to use only one set.
6. Tack/pin the top template/s against the datum line to cut one side of the fuselage. Pay attention that the centerline on the template is positioned between the two sides, the nose is at the squared edge. After one side is cut, the templates are flipped over for the cutting of the other side.
7. Make 1 or 2 sets of side profile template/s. Pay attention that they are placed over the datum line, the nose is at the squared edge. Hotwire cut along the side profile.
8. Cut the slots for wing seat, tail seat on the side profile template/s, cut out these slots on the whole foam assembly. 
9. For decks and turtledecks, cut slit/s on the side profile template/s, cut out these slits on the whole foam assembly. Make the section templates, position them into the slits, hotwire cut and remove the section templates.
10. Cut away cavity in the foam model.
11. Reinforce areas and points, install RC gears etc, glue together, sand external smooth, cover with tissue, paint and apply markings.
12. Attach pre-finished wings and tail pieces. 

Tubing

 3 May 2021

Tubing allows removal and adjustment, weighs a bit more.

Motor

Tubing on motor can slip onto rod motor mount or fuselage, and can pack to adjust angle slightly.

Wire on motor can be bent and tied to rod motor mount (or fuselage), but no point doing any packing to change angle

No point adjustable position on motor mount and fuselage.

Wings and tails

Tubing can allow removal.

Tubing can allow fore-aft adjustment, packing can lock in place.